This invention relates to repair of a recess in an article surface. More particularly, it relates to repair of a recess generated during operation of a power generating apparatus, for example a gas turbine engine.
During the operation of such power generating apparatus as a gas turbine engine, components in the gas stream, particularly in the hot operating portions, are subjected to strenuous operating conditions. Such conditions include a combination of oxidation and corrosion materials and gasses, erosive airborne particles, and mechanical actions resulting from rotation of the engine. As a result, it has been observed that one or more recesses are produced in a surface of components. Recesses, as used herein, include cracks, crevices, surface erosion, dents, indentations, separations, holes in or through the substrate, etc., commonly observed by those working in the repair of gas turbine engine components.
Current methods to repair recesses include application of repair material over the recess to fill and repair the recess. For example, material missing from a recess has been provided by applying and heating weld wire, metal powder mixed with a binder, and metal tapes and shims. Metal powders used for such a purpose include metal alloys and mixtures of metal or alloy powders, some of which are described in such U.S. Patents as U.S. Pat. No. 3,700,427--Hoppin et al. (patented Oct. 24, 1972); U.S. Pat. No. 3,759,692--Zelahy (patented Sep. 18, 1973); U.S. Pat. No. 4,004,047--Grisik (patented Jan. 18, 1977); U.S. Pat. No. 4,830,934--Ferrigno et al. (patented May 16, 1989); and U.S. Pat. No. 5,071,054--Dzugan et al. (patented Dec. 10, 1991).
The success of a repair using such materials has depended on the degree to which the repair material fills the recess. Forms of powder slurries with binders currently in use have been observed to separate and result in voids in a final structure. Inadequate filling can result in a porous article portion of reduced mechanical properties and integrity.